Serovar determination, drug resistance patterns and plasmid profiles of Pseudomonas aeruginosa isolated from burn patients at two hospitals of Tehran (IRAN)

Evaluation of Biofilm Formation and Frequency of Multidrug-resistant and Extended Drug-resistant Strain in Pseudomonas aeruginosa Isolated from Burn Patients in Isfahan

Background:

Pseudomonas aeruginosa is a biofilm-forming bacterium which can result in serious health problems, particularly in burn patients. Biofilm has been assumed to protect the bacteria from environmental fluctuations such as antimicrobial agent. Mucoid strains generate extensive levels of the alginate exopolysaccharide, which is an important factor of its biofilm.

Materials and Methods:

Totally, 100 isolates of P. aeruginosa has been gathered from wound infections of burn patients. Polymerase chain reaction of exoA gene has been carried out to confirm the bacteriologic identification of isolates. The biofilm-forming capacity has been specified by capsule staining and microtiter plate test as qualitative and quantitative determination, respectively. Antimicrobial susceptibility of the isolates has been specified by disk diffusion method.

Results:

All the isolates carried the exoA gene. The antibiotic resistance was imipenem (90%); levofloxacin (93%); aztreonam (87%); piperacillin-tazobactam (85%); tobramycin (92%); polymyxin b (PB) (2%); and ceftazidime (CAZ) (32%). Totally, multidrug-resistant (MDR) and extended drug-resistant (XDR) isolates were 19% and 75%, respectively. Fortunately, pan drug-resistant (PDR) strain has not been observed. The assessment of biofilm formation has shown that 7% of the isolates were nonbiofilm (N), weak (W) 67%, moderate (M) 22%, and strong (S) 4%.

Conclusions:

As a result, the findings of this survey indicated that PB and CAZ were the most effective antibiotics against P. aeruginosa, which of course indicate a serious problem about the emergence of the PDR strains. There was no relationship between the patterns of biofilm production and antibiotic susceptibility, but high frequency of MDR/XDR and biofilm producer strains has been detected.

Biofilm Formation and Virulence Factors Among Pseudomonas aeruginosa Isolated From Burn Patients

BACKGROUND

Pseudomonas aeruginosa possesses a variety of virulence factors and infections caused by multidrug-resistant P. aeruginosa (MDRPA) in burn patients are a public health problem.

OBJECTIVES

The aim of this study was to determine the antibiotic resistance pattern, the biofilm formation, the prevalence of MDRPA and two virulence genes (nan1 and exoA) among P. aeruginosa isolated from burn patients.

PATIENTS AND METHODS

A total of 144 isolates of P. aeruginosa were collected from burn patient at the Burn Centre of Tehran, Iran, between March 2013 and July 2013. Antibiotic susceptibility test was performed via agar disk diffusion method. The ability of producing biofilm was examined by crystal violet microtiter plate assay and the prevalence of the exoA and nan1 genes among the isolates was determined by polymerase chain reaction (PCR).

RESULTS

A high rate of resistance was seen against ciprofloxacin (93.7%), aztreonam (86.8%), piperacillin (85.4%), ceftazidime (82.6%), amikacin (82%) and imipenem (79.2%). In total, 93.1% of the isolates were characterized as MDRPA. Biofilm formation was seen in 92.4% of the isolates. The prevalence of the exoA and nan1 genes were 75% and 11.8% among the isolates, respectively.

CONCLUSIONS

The high rate of MDRPA and its ability to produce biofilm is an alarm for public health. The statistical analysis showed that biofilm production in the MDRPA isolates was significantly higher than that in the non-MDRPA isolates (P < 0.001).

Detection and Genetic Characterization of Metallo-β-Lactamase IMP-1 and VIM-2 in Pseudomonas aeruginosa Strains From Different Hospitals in Kermanshah, Iran

Background:

Pseudomonas aeruginosais a frequent nosocomial pathogen that causes severe diseases in many settings. Carbapenems, including meropenem and imipenem, are effective antibiotics against this organism. However, the use of carbapenems has been hampered by the emergence of strains resistant to carbapenemsvia different mechanisms such as the production of metallo-β-lactamases (MBLs), which hydrolyze all carbapenems. Several kinds of MBLs have been reported, among them VIM and IMP types being the most clinically significant carbapenemases.

Objectives:

We aimed to determine the distribution of bla_VIM-2 and bla_IMP-1 transferable genes encoding MBLs in P. aeruginosa isolated from three academic hospitals in Kermanshah.

Patients and Methods:

From 22nd June to 22nd September 2012, 225 isolates of P. aeruginosa were collected. These isolates were tested for antibiotic susceptibility with the Kirby-Bauer disk-diffusion method, and the MBLs were assessed using the imipenem-EDTA double-disk synergy test. The isolates were investigated for bla_VIM-2 and bla_IMP-1 genes using polymerase chain reaction.

Results:

Among the 225 isolates, 33.7% (76/225) and 18.1% (41/225) were resistant to imipenem and meropenem, respectively. Of the 76 imipenem-resistant P. aeruginosa strains, 45 (59.2%) were positive for MBLs, 34 (75%) strains carried the bla_IMP-1 gene, and 1 (2.2%) strain carried the bla_VIM-2 gene.

Conclusions:

Our results showed that there was a high frequency of IMP-1 positive P. aeruginosa in the different wards of the hospitals.

Plasmid mediated antibiotic resistance in isolated bacteria from burned patients

BACKGROUND

Nowadays, the treatment of burned patients is difficult because of the high frequency of infection with antibiotic resistance bacteria.

OBJECTIVES

This study was conducted to evaluate the level of antibiotic resistance in Gram-negative bacteria and its relation with the existence of plasmid.

MATERIALS AND METHODS

The samples were collected from two hundred twenty hospitalized burned patients in Isfahan burn hospital during a three-month period (March 2012 to June 2012). The samples were isolated and the Gram-negative bacteria were identified using phenotypic method and API 20E System. Antibiotic susceptibility and plasmid profile were determined by standard Agar disc diffusion and plasmid spin column extraction methods.

RESULTS

Totally 117 Gram-negative bacteria were isolated, the most common were Pseudomonas aerugionsa (37.6%), P. fluorescens (25.6%), Acinetobacter baumanii (20/5%) and Klebsiella pneumoniae (7.6%), respectively. The isolates showed high frequency of antibiotic resistance against ceftazidime and co-amoxiclave (100%) and low frequency of antibiotic resistance against amikacin with (70%).The results indicated that 60% of the isolates harboured plasmid. On the other hand, the patients infected with A. baumanii and P. aeruginosa were cured (with 60% frequency) whereas, those infected with P. fluorescens were not cured. Hence, probably antibiotic resistance markers of A. baumanii and P. aeruginosa are plasmid mediated; however, P. fluorescens is chromosomally mediated.

CONCLUSIONS

Based on our findings, P. aerugionsa is a major causative agent of wound infections and amikacin could be considered as a more effective antibiotic for treatment of the burned patients.

Profile of microorganisms and antimicrobial resistance at a tertiary care referral burn centre in Iran: emergence of Citrobacter freundii as a common microorganism

Infection and antimicrobial resistance are important issues in severe burn. The aims of this prospective study were to investigate the profile of microorganisms and resistance to antimicrobial agents in a tertiary referral burn centre; 113 people aged >10 years, with partial- or full-thickness burns, were included in the study. A total of 733 samples including 275 swabs, 164 tissue biopsies, 258 urine samples, 26 blood samples and 10 sputum samples were collected, from which 124 microorganisms were isolated. Pseudomonas aeruginosa and Citrobacter spp were the most prevalent isolates (57.3% and 35.5%, respectively); 95.5% of Citrobacter. isolates were Citrobacter freundii. Antibiogram results obtained from 15 antimicrobial agents demonstrated that imipenem was the most effective agent against P. aeruginosa, followed by ciprofloxacin and piperacillin/tazobactam (67.9%, 43% and 37.5% sensitive, respectively). At least 60% of all Citrobacter isolates were sensitive to various antimicrobial agents, the highest sensitivity being obtained by ceftazidime and cefepime (81.6% and 78.4%, respectively). Sensitivity of P. aeruginosa isolates to the agents of each antimicrobial class was significantly different (p<0.001). The incidence of C. freundii and the resistance of P. aeruginosa to anti-pseudomonas agents were exceptionally high.

Horizontal gene transfer in a polyclonal outbreak of carbapenem-resistant Acinetobacter baumannii

In the last few years, phenotypically carbapenem resistant Acinetobacter strains have been identified throughout the world, including in many of the hospitals and intensive care units (ICUs) of Australia. Genotyping of Australian ICU outbreak-associated isolates by pulsed-field gel electrophoresis of whole genomic DNA indicated that different strains were cocirculating within one hospital. The carbapenem-resistant phenotype of these and other Australian isolates was found to be due to carbapenem-hydrolyzing activity associated with the presence of the blaOXA-23 gene. In all resistant strains examined, the blaOXA-23 gene was adjacent to the insertion sequence ISAba1 in a structure that has been found in Acinetobacter baumannii strains of a similar phenotype from around the world; blaOXA-51-like genes were also found in all A. baumannii strains but were not consistently associated with ISAba1, which is believed to provide the promoter required for expression of linked antibiotic resistance genes. Most isolates were also found to contain additional antibiotic resistance genes within the cassette arrays of class 1 integrons. The same cassette arrays, in addition to the ISAba1-blaOXA-23 structure, were found within unrelated strains, but no common plasmid carrying these accessory genetic elements could be identified. It therefore appears that antibiotic resistance genes are readily exchanged between cocirculating strains in epidemics of phenotypically indistinguishable organisms. Epidemiological investigation of major outbreaks should include whole-genome typing as well as analysis of potentially transmissible resistance genes and their vehicles.

Antibiotic resistance and antibacterial activity in heterotrophic bacteria of mineral water origin

Antibiotic resistance and antibacterial activity were determined on heterotrophic bacteria isolated from mineral waters. Of the 120 isolates Pseudomonas spp. (55.8%) was the predominant group followed by Acinetobacter spp. (14.17%), Flavobacterium spp. (10.83%), Achromobacter spp. (10%), Burkholderia cepacia (3.3%), Agrobacterium/radiobacter (2.5%), Moraxella spp. (1.7%), Aeromonas hydrophila (1.7%). Over 80% of the isolates were resistant to one or more antibiotics and the highest resistance was found for chloramphenicol, ampicillin, colistin and sulfamethizole (60%, 55%, 50% and 47.5%, respectively). Strains with multiple antibiotic resistance (MAR) represented 55% of isolates and the most resistant organism belonged to the genus Pseudomonas. Of 40 randomly selected strains, 27 (67.5%) had antibacterial activity towards one or more indicators. This activity, found in a high percentage in the genus Pseudomonas (92%), emerged mainly against closely related microorganisms. Several producers were active also against Escherichia coli, Salmonella, Listeria monocytogenes and Staphylococcus aureus. Forty-six percent of the isolates harboured 1 to 5 plasmids with molecular weights ranging from 2.1 to 41.5 MDa.